/*
 * Copyright (C) 2018 Donlon.
 *
 * 2018秋季C语言练习题（1）
 * http://10.105.242.83/contest/412/
 *
 * C. 分制转换
 */

#include <stdio.h>

int main() {
    int grade;
    scanf("%d", &grade);
    
    char grade_char = 0;
    
    if (90 <= grade) {
       grade_char = 'A';
    } else if (80 <= grade) {
       grade_char = 'B';
    } else if (70 <= grade) {
       grade_char = 'C';
    } else if (60 <= grade) {
       grade_char = 'D';
    } else  {
       grade_char = 'E';
    }
    
    printf("%c", grade_char);
}
